Method for producing aminonaphthalene sulphonic acids

ABSTRACT

COMPOUNDS OF THE FORMULA   1-R,5-(HO3S-),7-NH2-NAPHTHALENE   IN WHICH R IS -OH OR -NH2 ARE PREPARED BY NITRATING 1-NITRONAPHTHALENE-5-SULFONIC ACID IN OLEUM TO GIVE 1,7DINITRONAPHTHALENE-5-SULFONIC ACID, REDUCING THE LATTER TO 1,7-DIAMINONAPHTHALENE-5-SULFONIC ACID AND OPTIONALLY EXCHANGING IN KNOWN MANNER THE 1-POSITIONED AMINO GROUP FOR A HYDROXY GROUP. THESE COMPOUNDS ARE USEFUL AS INTERMEDIATES IN THE PREPARATION OF AZOMETHINE DYESTUFFS, E.G. BY CONDENSATION WITH AROMATIC ALDEHYDES.

United States Patent 3,655,740 METHOD FOR PRODUCING AMINO- NAPHTHALENE SULPHONIC ACIDS Horst Nickel and Fritz Suckfiill, Leverkusen, Germany,

assignors to Farbenfabriken Bayer Aktiengesellschaft, 5

Leverkusen, Germany No Drawing. Filed July 22, 1968, Ser. No. 746,251

Claims priority, applicatigg Germany, July 31, 1967,

,106 Int. Cl. C07c 143/64, 143/56 US. Cl. 260-509 2 Claims 10 ABSTRACT OF THE DISCLOSURE Compounds of the formula HzN The object of the invention comprises new aminonaphthalene sulphonic acids of the formula in this formula R stands for a group OH or NH The new aminonaphthalene sulphonic acids are obtained by nitrating lnitronaphthalene-S-sulphonic acid in oleum at low temperatures up to about room temperature, preferably at temperatures of about 0 C. to about 30 C., to give 1,7-dinitronaphthalene-S-sulphonic acid, subsequently reducing the latter to 1,7-diaminonaphthalene- 5-sulphonic acid and optionally exchanging in the latter the l-positioned amino group for a hydroxy group, for example, by reaction with alkali metal bisulphites.

For example, sulphuric acid with a content of 10 to 30% S0 especially about 20% S0 is used as oleum for nitrating the 1nitronaphthalene-S-sulphonic acid. The individual nitration is carried out in such a manner that the 1nitronaphthalene-5-sulphonic acid is dissolved in oleum and reacted at temperatures, preferably below room temperature, e.g. at 10 C., with a nitrating agent, such as alkali metal nitrates, particularly potassium nitrate. The reaction is completed in the course of some hours. The desired 1,7-dinitronaphthalene-5-sulphonic acid can be isolated from the reaction mixture in such a way, for example, that the reaction mixture is poured on to ice and the resultant solution mixed with an inorganic salt, e.g. with potassium chloride, the 1,7-nitro compound being selectively precipitated. Other nitration products which may be present in the reaction mixture remain in solution.

The reduction of 1,7-dinitronaphthalene-S-sulphonic acid to 1,7diaminonaphthalene-S-sulphonic acid can be effected in conventional manner, e.g. with catalytically 3,655,740 Patented Apr. 11, 1972 excited hydrogen or with iron/acetic acid, or zinc/hydrochloric acid, or with alkali metal sulphides, or with alkali metal sulphites.

From the resultant 1,7-diaminonaphthalene-S-sulphonic acid there may then be prepared in known manner .the new 1hydroxy-7-aminonaphthalene-S-sulphonic acid by a Bucherer reaction, i.ee by the reaction with alkali metal bisulphites, such as sodium bisulphite, at temperatures, for example, ranging from C. to boiling temperature, followed by the customary working up by acidic -elimination of S0 and alkaline adjustment of the reaction mixture. The 1hydroxy-7-aminonaphthalene-S-sulphonic acid can be isolated from the reaction mixture by acidification and salting out, for example.

1,7-diaminonaphthalene-5-sulphonic acid and l-hydroxy-7-aminonaphthalene-S-sulphonic acid are new products which are suitable for various purposes of application. They can be used as additives to lubricating substances and as intermediates for the synthesis of optical brighteners, plant protectants and azomethine dyestuffs. The latter are obtained by condensing aromatic aldehydes with aminonaphthalene sulphonic acid.

The process for the preparation of the new aminonaphthalene sulphonic acids described above proceeds in a surprising manner in so far as the nitration of l-nitronaphthalene-S-sulphonic acid according to the previously known method, e.g. in sulphuric acid, preponderantly or exclusively leads to 1,S-dinitronaphthalene-S-sulphonic acid. It could not be expected that the nitration of l- 0 nitronaphthalene-Ssulphonic acid in oleum, particularly under the afore-mentioned conditions, would lead to the likewise unknown 1,7-dinitronaphthalene 5 sulphonic acid.

EXAMPLE 50.6 parts (0.2 mol) 1-nitronaphthalene5-sulphonic acid are introduced at 10 to 15 C., with stirring and external cooling, into 400 parts by volume oleum (with a content of 20% S0 Into this solution 22 parts of finely powdered potassium nitrate are subsequently slowly strewn in at 10 to 12 C., with external cooling, and stirring is continued for 3 hours without further cooling, the temperature slowly rising to room temperature. The reaction mixture is then poured on to about 2000 parts of ice; temperature about 20 C. The resultant pale brown solution is mixed with about 10% of its volume potassium chloride and stirred overnight. The precipitated 1,7-dinitronaphthalene-S-sulphonic acid is filtered 01f with suction.

The paste obtained is introduced at 96 to 100 C. into a mixture of 70 parts iron chips, 500 parts by volume of water and 25 parts glacial acetic acid and stirred for about one hour. The mixture is subsequently rendered alkaline with about parts of a 20% sodium carbonate solution and filtered off with suction from the iron slurry while hot. The filtrate contains the 1,7-diaminonaphthalene-S-sulphonic acid. By acidification with hydrochloric acid and mixing with sodium chloride, 1,7-diaminonaphthalene-S-sulphonic acid is separated in solid form and isolated.

The resultant sodium salt of 1,7-diaminonaphthalene- 5-sulphonic acid is readily soluble in water and has a blue-green fluorescence under ultra violet irradiation.

In order to convert the 1,7-diaminonaphthalene-5- sulphonic acid into 1-hydroxy-7-aminonaphthalene-S- sulphonic acid, 0.1 mol of the acidic paste of the diamino compound is mixed by stirring with 200 parts by volume of a 40% sodium bisulphite solution and kept at 10-5 to 108 C. (for about 9 hours) until the diamino compound can no longer be detected. The mixture is subsequently rendered acid to congo at 50 to 80 C. with about 80 parts 30% hydrochloric acid and subsequently stirred until S can no longer be detected. A pH is then adjusted with a sodium hydroxide solution and the mixture kept at 90 to 100 C. for a further 30 minutes and then acidified with hydrochloric acid at C. After stirring the mixture until cold, the precipitated l-hydroxy- 7-aminonaphthalene-5sulphonic acid is filtered oil? with suction.

The Na salt of this acid is readily soluble in water and has a green fluorescence under ultra violet irradiation.

We claim:

1. Process for the preparation of compounds of the formula oleum at temperatures of about 0-30 0.;

4 (b) subjecting the resulting 1,7-dinitronaphthalene-5- sulfonic acid to reduction to form 1,7-diamino-5- sulfonic acid; and

where R is OH the additional step (c) comprising reacting said 1,7-diaminonaphthalene-S-sulfonic acid with an alkali metal bisulfite at C. to boiling temperature and rendering the mixture acid. 2. The process of claim 1 wherein the nitrating step (a) is carried out in 10-30% oleum.

References Cited UNITED STATES PATENTS 2,748,107 5/1955 Hendrickson et a1. 260-144 FOREIGN PATENTS 82,676 2/1894 Germany 260509 OTHER REFERENCES Beilstein, Handbuch der Organischen Chemie, Vierte 20 Auflage, Tweites Ergantzungswerk General Formel Register, pp. 796, 797, 817, 818 (1956).

DANIEL D. HORWITZ, Primary Examiner US. Cl. X.R. 260--510 

